The present invention relates to snowmobiles and in particular to a slide rail, track drive assembly including a hollow enclosure having side mounted slide rails and about which the endless drive track is mounted and whereby snow and ice build up inside the track is prevented.
Snowmobile track systems are typically driven by a sprocket and chain that are coupled via an intermediate clutch assembly to the engine crank shaft and thence to a mating sprocket driven axle and upon which a pair of track engaging sprockets are mounted so as to cause the track to revolve. Multiple pairs of idler wheels are, in turn, mounted behind the drive sprockets on each side of the track and are coupled to a frame assembly interior to the revolving endless track so as to establish an elongated and supported track contour of sufficient surface area to support the chassis and operator. An example of a typical snowmobile of this type can be seen upon reference to U.S. Pat. No. 4,314,618, assigned to the present assignee.
By leaving the space internal to the track open, however, problems can occur during use, depending upon the snow and weather conditions, through the build up of snow and ice therein. The snow and ice either hampering the operation of the idler sprockets or idler wheels or creating drag due to the added weight. Accordingly, it is an object of the present invention to minimize this potential snow and ice build up through the use of a hollow-framed enclosure in the space internal to the track. Thus, the hollow enclosure now occupies the previously empty space. The track supporting drive sprockets and idler wheels are, in turn, mounted to the sides of the enclosure or on axles passing therethrough in lieu of on a barstock frame.
It is a further object of the present invention to incorporate a slide rail assembly about the side edges of the hollow enclosure and about which the track is supported and revolves. The slide rails are mounted to the enclosure and mate with metal guide clips that are mounted in a space between the various belts to coated rods that join the belts together. The guide clips are also formed so as to mate with the side rails and contain the enclosure in the center of the track via the side forces exerted by the clips against the slide rails.
Additionally, the present invention contemplates a pivotally mounted, shock absorbing suspension system that is coupled between the hollow-framed enclosure and the snowmobile chassis so as to absorb and minimize the transfer of any induced vibration or shock to the driver. A pair of forward ski related shock absorbers further absorb any shock induced at the front end of the machine and thus a relatively smooth ride is obtained.
Partially enclosed wheel supported track systems have previously been used in conjunction with snow vehicles and examples of which can be found upon reference to U.S. Pat. Nos. 2,702,008 and 2,561,716. However, such assemblies differ from the present assembly in that the '088 Patent contemplates a housing which surrounds not only the space interior to the track but also the engine, thereby requiring ventilation louvers. The '716 patent, on the other hand, is directed to a snow tractor that receives it track drive via a drive shaft, thus requiring an opening through the hollow enclosure to the drive sprockets. Neither of such patents, however, disclose a slide rail drive assembly in conjunction with the enclosure. Additionally, it is to be noted that U.S. Pat. Nos. 3,877,534 and 4,314,618 disclose the use of shock absorber suspension systems and that U.S. Pat. No. 4,301,884 discloses a track that is pivotally mounted to the chassis, but which as will become apparent, too, are different from the present combination.